As is well known to those skilled in the art, window channel weatherstripping materials have traditionally been made from ethylene-propylene-diene terpolymers (EPDM) or thermoplastic elastomers (TPE). A thermoplastic elastomer is defined as a mechanical blend of fully or partially cross-linked rubber and thermoplastic material. One of the problems with these materials, however, is that they present too much friction relative to glass and as a result stick to glass. This stickiness to glass interferes with movement of the glass with respect to the weatherstripping and also contributes to a breakdown and degradation of the weatherstripping material. That problem has traditionally been overcome by flocking the surfaces of the weatherstripping material which reduces the friction and thereby eliminates sticking.
The flocking process adds several steps to the manufacturing process including (1) abrading the weatherstripping surface; (2) applying adhesive; (3) applying flocking; and (4) baking.
Recently, a variety of approaches have been taken to obviate the need for flocking. For example, European Patent No. 0 325 830 A2 teaches a coextruded blend of EPDM and a wear resistant thermoplastic such as polypropylene; French Patent No. 2,580,285 teaches a coating of low friction or self-lubricating material such as high molecular weight polyethylene; Japanese Patent No. 58/042,624 teaches a lubricant layer comprising crosslinked elastomer binder and a lubricating powder; West German Patent No. 3,405,973 teaches sealing strips composed of a rubber or elastomer and plastic or woven textile strip which are coextruded; and Japanese Patent No. 61/104,842 teaches a rubbery elastomer comprising a rubbery elastomer substrate, a nylon resin film, and a primer layer set between them. The primer layer is composed of chlorinated polypropylene, acid anhydride, epoxy resin, and an amine curing agent.
A low friction, abrasion resistant polymer coating would present several advantages over flocking. A more intimate contact between the weatherstripping and the glass would be achieved. Furthermore, such a coating could be coextruded with the weatherstripping material. Additionally, a coating being all polymeric would be more environmentally safe because such a coating would obviate the need for solvent-based adhesives now used with flocking.
A need still exists for a low friction, abrasion resistant coating with good adhesion to the weatherstripping material and good elasticity to prevent breaking upon flexing. Additionally, the coating should exhibit ultraviolet stability and a broad service temperature range.